1. Field of the Invention
The present invention relates to an intake manifold in a multi-cylinder internal combustion engine wherein the manifold is designed to super-charge an air-fuel mixture by an inertia effect. The present invention also relates to a connecting method for branch pipes of such an intake manifold.
2. Description of the Related Art
An inertia charge intake manifold includes a surge tank and a plurality of branch pipes for connecting the surge tank to the cylinder head of a multi-cylinder internal combustion engine. Each of the branch pipes needs to be relatively long for utilizing the inertia effect of the gas flow for supercharging. Further, all of the branch pipes need to be substantially equal in length for equalizing the inertia effect within the respective branch pipes.
JP-U-1(1989)-99965 discloses an inertia charge intake manifold which is made of a metal such as aluminum or suitable alloy. The intake manifold includes a surge tank located remote from the cylinder head of a multi-cylinder internal combustion engine, and a plurality of relatively long branch pipes connecting the surge tank to the cylinder head. The surge tank is located remote from the cylinder head to provide a long path for arranging the relatively long branch pipes without sharply bending.
However, since the surge tank is located remote from the cylinder head, the engine combined with the intake manifold becomes inevitably bulky. Further, difficulty arises in supporting the surge tank on the engine particularly in view of the fact that the surge tank itself must support other intake components such as a throttle body or carburetor which is relatively heavy. Indeed, a large tough support bracket is necessary for this purpose, which results in an increase of cost and weight. Still further, since the conventional manifold is made of aluminum for example, the branch pipes tend to have rather rough inner surfaces which may cause the flow resistance within the branch pipes to become unfavorably high.
It is, therefore, an object of the present invention to provide an intake manifold which is capable of eliminating or at least reducing the problems of the prior art described above.
Another object of the present invention is to provide a method of connecting the branch pipes of an intake manifold to a surge tank or to a common flange.
According to the present invention, there is provided an inertia charge intake manifold in an internal combustion engine having a plurality of cylinders. The intake manifold includes:
elongated separate branch pipes each corresponding to a respective one of the cylinders;
a common flange for connecting a first end of each branch pipe to the internal combustion engine; and
a surge tank to which a second end of said each branch pipe is connected;
wherein the common flange, the surge tank and said each branch pipe are made of a hard thermoplastic synthetic resin, the common flange being integrally connected to the surge tank.
In the above arrangement, since the common flange and the surge tank are integrally connected to each other, the surge tank is directly supported by the common flange. Thus, the intake manifold as a whole can be reduced in size, as compared with the conventional intake manifold.
Further, according to the above arrangement, the overall weight of the intake manifold is advantageously reduced, since the common flange, the surge tank and the respective branch pipes are made of a resin material. In addition, with the use of a resin material, the inner surfaces of the respective branch pipes can be rendered smoother than is conventionally possible, thereby reducing the flow resistance within each branch pipe.
According to a preferred embodiment, the surge tank may have an external side surface, and the common flange may be arranged to extend generally in parallel to the external side surface of the surge tank.
With such an arrangement, the connection area between the surge tank and the common flange can be rendered comparatively large. In this manner, it is possible to increase the strength by which these two members are bonded to each other.
Preferably, said each branch pipe may be bent so that the first end is horizontally oriented and the second end is upwardly oriented. The horizontally-oriented first end may be fitted into a connecting bore formed in the common flange, while the upwardly oriented second end may be fitted into a receiving bore formed in an underside surface of the surge tank.
With such an arrangement, each branch pipe can hold on to the common flange and the surge tank without using fixing means such as an adhesive.
Preferably, the first end of said each branch pipe may be integrally formed with a cylindrical protrusion which is nonremovably fitted into a connecting bore formed in the common flange. The common flange may be provided with a connection surface attached to the internal combustion engine. The connection surface may be provided with a circular hollow portion extending around the cylindrical protrusion of said each branch pipe. The circular hollow portion may be arranged to accommodate a ring-shaped sealing member in a manner such that the sealing member partially projects beyond the connection surface of the common flange.
Advantageously, the first end of said each branch pipe may be provided with a brim coming into contact with the common flange.
According to a second aspect of the present invention, there is provided a method of connecting an end of a branch pipe of an intake manifold to another member of the intake manifold, wherein the branch pipe and said another member are made of a hard thermoplastic synthetic resin. The method includes the steps of:
providing the end of the branch pipe with a flat end surface which is generally perpendicular to an axis of the end of the branch pipe;
providing said another member with a connecting surface for fixing the flat end surface;
forming a ring-shaped protrusion on at least one of the flat end surface and the connecting surface;
arranging a heating wire around the ring-shaped protrusion;
causing the flat end surface and the connecting surface to be pressed against each other; and
applying a voltage across the heating wire.
The above method may further comprise the step of arranging a ring-shaped seal member made of an elastic material between the ring-shaped protrusion and the heating wire. In this method, the voltage applying step may be performed when the seal member is pressed.
According to a third aspect of the present invention, there is provided a method of connecting an end of a branch pipe of an intake manifold to another member of the intake manifold, wherein the branch pipe and said another member are made of a hard thermoplastic synthetic resin. The method includes the steps of:
providing said another member with a connecting bore;
providing the end of the branch pipe with a cylindrical protrusion to be inserted into the connecting bore and with a brim integral with the cylindrical protrusion;
arranging a heating wire circumferentially of the connecting bore;
inserting the cylindrical protrusion into the connecting bore so that the heating wire is located adjacent to a boundary between the cylindrical protrusion and the brim of the branch pipe;
causing the brim of the branch pipe and said another member to be pressed against each other; and
applying a voltage across the heating wire.
The present invention will now be described further, by way of example, on the basis of the preferred embodiment given with reference to the accompanying drawings.